1 // Copyright 2025, Google Inc.
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29 30 package gax
31 32 import (
33 "os"
34 "strings"
35 "sync"
36 )
37 38 var (
39 // featureEnabledOnce caches results for IsFeatureEnabled.
40 featureEnabledOnce sync.Once
41 featureEnabledStore map[string]bool
42 )
43 44 // IsFeatureEnabled checks if an experimental feature is enabled via
45 // environment variable. The environment variable must be prefixed with
46 // "GOOGLE_SDK_GO_EXPERIMENTAL_". The feature name passed to this
47 // function must be the suffix (e.g., "FOO" for "GOOGLE_SDK_GO_EXPERIMENTAL_FOO").
48 // To enable the feature, the environment variable's value must be "true",
49 // case-insensitive. The result for each name is cached on the first call.
50 func IsFeatureEnabled(name string) bool {
51 featureEnabledOnce.Do(func() {
52 featureEnabledStore = make(map[string]bool)
53 for _, env := range os.Environ() {
54 if strings.HasPrefix(env, "GOOGLE_SDK_GO_EXPERIMENTAL_") {
55 // Parse "KEY=VALUE"
56 kv := strings.SplitN(env, "=", 2)
57 if len(kv) == 2 && strings.ToLower(kv[1]) == "true" {
58 key := strings.TrimPrefix(kv[0], "GOOGLE_SDK_GO_EXPERIMENTAL_")
59 featureEnabledStore[key] = true
60 }
61 }
62 }
63 })
64 return featureEnabledStore[name]
65 }
66 67 // TestOnlyResetIsFeatureEnabled is for testing purposes only. It resets the cached
68 // feature flags, allowing environment variables to be re-read on the next call to IsFeatureEnabled.
69 // This function is not thread-safe; if another goroutine reads a feature after this
70 // function is called but before the `featureEnabledOnce` is re-initialized by IsFeatureEnabled,
71 // it may see an inconsistent state.
72 func TestOnlyResetIsFeatureEnabled() {
73 featureEnabledOnce = sync.Once{}
74 featureEnabledStore = nil
75 }
76